Electrical power supply



Sept. 30, 1958 G. o. CROWTHER 2,854,618

ELECTRICAL POWER SUPPLY Filed March 28, 1956 I l8 l8 6 5 f J l9 n3 9 IO 7 E LOAD "'1 INVENTOR GERALD OFFLEY CROWTHER AGENT United States Patent ELECTRICAL rowER SUPPLY Gerald Ofiley Crowther, Cheam, England, assignor, by

mesne assignments, to North American Philips Company, Inc., New York, N. Y., a corporation of Delaware Application March 23, 1956, Serial No. 574,404

Claims priority, application Great Britain May 13, 1955 4 Claims. (Cl. 323-22) The present invention relates to a voltage stabilizer circuit. More particularly, the invention relates to a voltage stabilizer circuit having a substantially direct voltage input and an output voltage capable of being switched from one stabilized and preset direct current voltage to another stabilized and preset direct current voltage. The present invention is an improvement in the circuit described in U. S. Patent No. 2,752,555, issued June 26, 1956, to Light. Patent No. 2,752,555 describes a voltage stabilizer circuit capable of being switched from one stabilized and preset direct current output voltage to another stabilized and preset direct current output voltage comprising a variable impedance connected between an input terminal and an output terminal, means for producing a plurality of fractions of the output voltage, each fraction being independently preset, and further means enabling each of the fractions at separate times to be compared with a reference voltage, the result of the comparison being used to influence said variable impedance so as to cause the output voltage to stabilize at a value corresponding to the fraction being compared.

If a load having a capacitive component, for example due to stray capacitance, is connected to the output terminals it will be appreciated that, when it is desired to change the output voltage from a higher voltage to a lower voltage, the maximum rate of change will not exceed that due to the time constant of the load.

An object of the present invention is to provide a circuit which mitigates this disadvantage.

According to the invention a voltage stabilizer circuit as described in U. S. Patent No. 2,752,555, adapted for use with a load having a capacitive component, is provided with discharging means between the output terminals, which discharging means is conductive only while the output voltage is in transition from one voltage to a lower voltage.

Preferably the discharging means comprises a grid controlled high vacuum electric discharge tube connected substantially between the output terminals. Said tube is held non-conductive by bias except when rendered conductive during said transition by a positive going pulse applied to the control grid. The positive going pulse may be obtained from the means enabling each of the fractions at separate times to be compared with a reference voltage.

In order that the invention may be readily carried into eifect it will now be described with reference, by way of example, to the accompanying drawing in which the single figure is a schematic diagram of the voltage stabilizer circuit arrangement of the present invention.

Referring to the figure of the present invention, a series electric discharge tube 1 is connected in the positive lead 18, 18 between an input terminal 19 and an output terminal 20. Across the input terminals 19, 19 is connected the combination of a resistor 7, first and second electric discharge tubes 2 and 3 respectively, having their anodes and cathodes connected in parallel and "ice a reference voltage source in the form of a neon stabilizer tube 8. The resistor 7 is the common anode load of the tubes 2 and 3, the voltage developed across it being applied to the control grid of the tube 1.

A resistor 9 is provided in parallel with resistor 7 and tubes 2 and 3 to ensure that the neon stabilizer tube 8 is kept ignited. The control grid 4 of tube 2 is supplied from the junction of a variable resistor 11 and a fixed resistor 1?. of a resistor chain 10, 11 and 12 connected across the output terminals 20, 20.

The voltage of the control grid 4 is a proportion of the output voltage and the proportion may be varied between limits by variation of the resistor 11. The control grid 5 of tube 3 is similarly supplied from the resistor chain 13, 14 and 15 with the exception that another resistor 16 is interposed between the junction of resistors 14 and 15 and the control grid 5. This resistor to acts as part of the anode load of a keying tube 17 connected between the control grid 5 and ground. The tube 17 is caused to be conductive or non-conductive by the application of a voltage to its control grid via terminals 21, 21.

The proportion of voltage supplied to grid 4 is less than that supplied to grid 5 so that when the keying tube 17 is non-conductive, tube 3 is conductive and tube 2 is non-conductive, whereas when the tube 17 is conductive the voltage of control grid 5 falls well below the cathode voltage determined by neon stabilizer tube 8 and tube 3 becomes non-conductive and tube 2 becomes conductive.

To the input terminals 19, 19 is connected a substantially direct current source of supply which may be in the form of a power pack supplied from the alternating current supply source and may comprise a transformer, rectifier and smoothing filter.

This circuit arrangement is modified in accordance with the present invention by the addition of a triode 22 having its anode connected to the cathode of tube 1, its control grid connected to the anode of tube 17 and its cathode connected to the junction of a voltage divider connected between the anode of tube 1 and ground and formed by resistor 23 in series with a resistor 24. Resistor 24 is shunted by a bypass capacitor 25. The voltage divider 23, 24 provides a positive bias voltage for the cathode of tube 22 so that it remains nonconductive in the quiescent condition.

T he ciricuit operates as follows:

When the keying tube 17 is cut-01f, tube 3 is conducting, tube 2 is non-conducting and output voltage is at the lower of the two preset voltages and is stabilized.

To show that stabilization takes place, it may be suppose-d that the voltage across the terminals 20, 20 decreased slightly. Then the voltage at grid 5 decreases, the anode current of tube 3 decreases, the voltage at the anode of tube 3 increases, the grid of tube 1 causes the impedance of tube 1 to decrease so that the voltage across terminals 20, 2t} increases to counteract the supposed voltage decrease.

To preset the lower voltage at the desired value, the variable resistor 14 is adjusted.

Then keying tube 17 is made to conduct causing tube 3 to be non-conducting and the output voltage to rise until tube 2 takes over. Now the output voltage across terminals 20, 20 is stabilized in like manner, but at the higher voltage which is adjustable within limits by varying the setting of variable resistor 11.

When the keying tube 17 is again made non-conducting, tube 3 becomes conducting causing the output voltage to decrease which, in turn, causes tube 2 to be nonconducting.

Thus by merely making keying tube 17 become conduc- 3 tive or non-conductive the output voltage is switched from a lower stabilized voltage to a higher stabilized voltage and vice-versa.

Now when tube 17 is made conductive its anode falls in voltage, the grid of tube 22 falls with it and tube 22 remains non-conductive. However, as already explained, the output voltage rises to the new stabilized voltage and accordingly the voltage at the junction of resistors 14, and 16 also rises, so that when tube 17 is again made non-conductive the voltage of the anode of tube 17 and the grid of tube 22 rises towards the voltage of the junction of resistors 14, 15 and 16. This makes tube 22 conductive and thus able to discharge the capacitive component of a load connected between terminals 20, 20. The output voltage falls to the lower voltage which is stabilized by control tube 3, and with it falls the voltage of the grid of tube 22 until it (tube 22) again becomes non-conductive. Thus tube 22 is conductive only during a transition from a higher stabilized voltage to a lowerstabilized voltage and serves to discharge the capacitive components of a load across terminals 20, 20 thereby enabling a quicker transition:

The portion of the circuit comprising components 22 to 25 inclusive may be connected in similar manner to the circuit shown in Figure 2 of U. S. Patent No. 2,752,555 with equal advantage.

While the invention has been described by means of a specific example and in a specific embodiment, I do not wish to be limited thereto, for obvious modifications will occur to those skilled in the art without departing from the spirit and scope of the invention.

What is claimed is:

1. A voltage stabilizer circuit capable of being switched from one stabilized and preset direct current output voltage to another stabilized and preset direct current output voltage, said circuit having a pair of output terminals, and a load having a capacitive component connected between said output terminals, comprising a variable impedance connected between an input terminal and an output terminal of said circuit, means for producing a plurality of fractions of the output voltage, each fraction being independently preset, means enabling each of the fractions at separate times to be compared with a reference voltage, the result of the comparison being used to influence said variable impedance so as to cause the output voltage to stabilize at a value corresponding to the fraction being compared, discharge means connected between said output terminals, and means for rendering said discharge means conductive during the transition of the output voltage from one value to another value of relatively lower magnitude.

2. A voltage stabilizer circuit capable of being switched from one stabilized and preset direct current output voltage to another stabilized and preset direct current output voltage, said circuit having a pair of output terminals, and a load having a capacitive component connected between said output terminals, comprising a variable impedance connected between an input terminal and an output terminal of said circuit, means for producing a plurality of fractions of the output voltage, each fraction being independently preset, means enabling each of the fractions at separate times to be compared with a reference voltage, the result of the comparison being used to influence said variable impedance so as to cause the output voltage to stabilize at a value corresponding to the fraction being compared, discharge means comprising a grid-controlled electron discharge device connected between said output terminals, means for normally maintaining said discharge device non-conductive, and means for rendering said discharge device conductive during the transition of the output voltage from one value to another value of relatively lower magnitude.

3. A voltage stabilizer circuit as claimed in claim 2, wherein said means for normally maintaining said discharge device non-conductive applies a substantially positive bias to the cathode of said discharge device and said means for rendering said discharge device conductive applies a positive pulse to the grid of the said discharge device.

4. A voltage stabilizer circuit capable of being switched from one stabilized and preset direct current output voltage to another stabilized and preset direct current output voltage, said circuit having a pair of output terminals, and a load having a capacitive component connected between said output terminals, comprising a variable impedance connected between an input terminal and an output terminal of said circuit, said variable impedance comprising a first electron discharge tube having a grid, means for producing a plurality of fractions of the output voltage, each fraction being independently preset, means enabling each of the fractions at separate times to be compared with a reference voltage, the result of the comparison being used to influence said variable impedance so as to cause the output voltage to stabilize at a value corresponding to the fraction being compared, said last-mentioned means comprising the arrangement of first and second control tubes each having a cathode, an anode and a grid, the two control tubes having a common anode circuit and a common cathode circuit, the common anode circuit being connected to the grid of said first discharge tube and the common cathode circuit comprising the source of said reference voltage, a pair of resistor chains each connected across said output terminals and providing one of said fractions, the control grid of each of said control tubes being connected to a point on a separate resistor chain, and a keying device comprising a second electron discharge tube having an anode, the arrangement being such that when in operation said first control tube determines the output voltage of relatively higher magnitude and said second control tube determines the output voltage of relatively lower magnitude, said second discharge tube being connected in the grid circuit of said second control tube in such a manner that said keying device determines when the said second control tube is conductive, discharge means comprising a third electron discharge tube having a grid, said third discharge tube being connected between said output terminals, means for normally maintaining said third discharge tube non-conductive, and means for rendering said third discharge tube conductive during the transition of the output voltage from said output voltage of relatively higher magnitude to said output voltage of relatively lower magnitude comprising means connecting the grid of the said third discharge tube to the anode of said second discharge tube.

Poch Sept. 9, 1947 Light June 26, 1956 

